The animal with the largest brain relative to its body size is the sperm whale. Though sperm whales are the largest toothed animals, their brain size is particularly notable for being the heaviest of all animals, weighing about 17 pounds (7.8 kilograms) on average. This impressive brain is an adaptation to their complex social behaviors, sophisticated communication skills, and deep-diving hunting techniques. While brain size in general does not directly correlate with intelligence, sperm whale brains are believed to play an important role in their advanced cognitive functions and social structures within pods.